Refrigeration system with multiple motor and crankshaft compressor



Jan. 6, 1970 A. F. TEEGARDEN ,657

REFRIGERATION SYSTEM WITH MULTIPLE MOTOR AND CRANKSHAFT COMPRESSOR .2 Sheets-Sheet 1 Filed Dec. 4, 1968 FIG. 5

INVENTOR.

ARLO F. TEEGARDEN BY WWW ATTORNEY Jan. 6, 1970 A. F. TEEGARDEN 3,487,657

REFRIGERATION SYSTEM WITH MULTIPLE MOTOR AND CRANKSHAFT COMPRESSOR Filed Dec. 4, 1968 .2 Sheets-Sheet a /IIIIIIIIIIIIJIIIIIIIII k. 4 5

III4VIIIIJI VIIIIIIIIIII j K53 A INVENTOR.

FIG. 4 I ARLo F. TEEGARDEN ATTORNEY United States Patent REFRIGERATION SYSTEM WITH MULTIPLE MOTOR AND CRANKSHAFT COMPRESSOR Arlo F. Teegarden, Onalaska, Wis, assignor to The Trane Company, La Crosse, Wis., a corporation of Wisconsin Filed Dec. 4, 1968, Ser. No. 781,058 Int. Cl. F25!) 1/02; F04b 35/04, 27/04 US. Cl. 62-229 9 Claims ABSTRACT OF THE DISCLOSURE A vapor compression refrigeration system using a reciprocal compressor having two crankshafts disposed within a common crankcase, plural drive motors for each of the crankshafts, and means for varying the capacity of the refrigeration system by selectively operating the plural drive motors and crankshafts.

BACKGROUND OF THE INVENTION This invention relates to vapor compression refrigeration systems. More particularly this invention relates to vapor compression refrigeration systems employing reciprocal type refrigerant compressors driven by electric motor means.

There is a growing tendency today for refrigeration systems to be constructed with air cooled condensers because of the general water shortages that exit throughout the world. However, refrigeration systems operating with air cooled condensers must generally operate at higher temperatures and pressures than comparable water cooled refrigeration sytems. In such refrigeration systems it is generally necessary to maintain sufiiciently low suction pressure to obtain the desired cooling temperature. The net result is that air cooled refrigeration systems must be operated with higher compression ratios than water cooled refrigeration systems. In such refrigeration systems herein, it is more costly to obtain these higher compression ratios in relatively small centrifugal compressors. Since centrifugal refrigeration compressors are generally used in the larger systems and reciprocal compressors in smaller systems, there is a growing tendency for reciprocal compressors to be used in larger systems where the condenser is air cooled.

There are few manufacturers of refrigerant reciprocating compressors in sizes over 100 tons. To obtain larger tonnages with reciprocal compressors, it is a common practice to duplex or parallel compressors. However, serious lubrication problems may arise where less than all the compressors are operated as the lubricating oil may collect in the nonoperating compressor thereby starving the operating compressors of vital lubrication.

SUMMARY OF THE INVENTION It is therefore an object of this invention to provide a reciprocal type refrigerant compressor which can be constructed in the larger sizes such as 100 tons or more which utilizes the running gear and standard parts of smaller compressors.

It is another object of this invention to provide a refrigeration system which is driven by plural motors of smaller size which may be mass produced at a lower cost. It is still a further object of this invention to provide a refrigeration system having multiple motors and crankshafts whereby the capacity of the refrigeration system may be controlled by operating less than all of said crankshafts and motors without creating lubricating problems.

Other objects and advantages may become apparent as this specification proceeds to describe the instant invention with reference to the drawings in which:

FIGURE 1 is a perspective view of my novel refrigeration compressor shown schematically connected to a refrigeration system;

FIGURE 2 is a vertical transverse section of the compressor of FIGURE 1;

FIGURE 3 is a horizontal section taken at about line 33 of FIGURE 2;

FIGURE 4 is a section taken at line 4-4 of FIG- URE 2;

FIGURE 5 is a control circuit which may be used to operate the refrigeration system of FIGURE 1 to obtain capacity control.

Now with reference to the drawings and particularly 'FIGURE 1 it will be seen that refrigeration system 10 is arranged to cool space 12 and includes an air cooled refrigerant condenser 14, a refrigerant throttling means such as expansion valve 16, a refrigerant evaporator 18 disposed in heat exchange relation with space 12, and a refrigerant compressor 20 respectively serially connected in a closed refrigerant loop 21.

Compressor 20 is shown in FIGURES 1, 2, 3, and 4, and has a main housing 22. Housing 22 includes a central compressor section 24 and a motor housing section 26 at each end of compressor section 24. The compressor section of housing 22 has a single crankcase chamber 28 which defines a single oil sump at the bottom thereof. Crankshafts 30 and 32 disposed within crankcase chamber 28 are mounted for rotation in bearings 34 for rotation about parallel horizontal axes. Each of crankshafts 30 and 32 has a first throw and a second throw angularly displaced from said first throw by Crankshaft 30 is drivingly connected to motor 36 at one end and drivingly connected to motor 38 at the other end. Crankshaft 32 is drivingly connected to motor 40 at one end and drivingly connected to motor 42 at the other end. Each of the motor sections 26 of housing 22 are provided with a suction inlet opening 44 (only one is visible) for receiving refrigerant gas returning from evaporator 18 via refrigerant loop 21. Cool suction gas returning to compressor 20 from evaporator 18 by way of openings 44 thus serv to cool motors 36, 38, 40 and 42.

The compressor section 24 of housing 22 may be formed by connecting two substantially allochiral sections 46 and 47 as by bolts 49. In the embodiment shown each of sections 46 and 47 has three cylinder banks 48 each having a pair of compression cylinders 50. Each cylinder is parallel to the other cylinder of said pair of cylinders. One cylinder of each pair is coextensive with one throw of a crankshaft while the other cylinder of said pair is coextensive with the other throw of said crankshaft in the direction of the crankshaft axis. Each of cylinders '50 extends radially of the axis of the crankshaft within its respective compressor section 46 or '47 and is disposed above a horizontal plane extending through the axes of crankshafts 30 and 32. Mounted for reciprocal movement within each of cylinders 50 is a piston 52 for compressing refrigerant gas within the cylinder. Each piston 52 s drivingly connected to the crankshaft within the respective compressor section 46 or 47 by a connecting rod 54 whereby rotation of the crankshafts serves to compress refrigerant gas within each of cylinders 50. Rods 54 may be connected to the crankshafts through access opening subsequently by panels 41. Refrigerant gas passing through openings 44 of each motor section 26 passes over the motors within the respective motor section 26 through passages 51 (only partially shown) to each of the cylinders 50 via the suction chamber 43 of each cylinder bank head 45 and suction valves 53. Passages 51 are also connected to drain oil accumulated therein to crankcase chamber 28. Gas compressed within cylinders 50 passes through discharge valves 54 into the discharge chamber 55 of each head 45 into passages 57 (only partially shown) within each of sections 46 to outlet openings 56 (only one shown) which are connected to the inlet condenser 14.

During operation of the compressor refrigerant is compressed within compressor 20 and conducted by way of refrigerant loop 21 to condenser 14. Cooling air passing over condenser 14 causes the refrigerant there within to condense at the high pressure. The refrigerant condensate is throttled by way of expansion valve 16 to a lower pressure into evaporator 18. The refrigerant condensate evaporates within evaporator 18 by absorbing heat from the surrounding space 12. The evaporated refrigerant is then again returned to compressor 20 by way of loop 21 for recirculation. The temperature within space 12 may be regulated by a thermostat 58 which includes a sensing bulb 59 responsive to the temperature of space 12 connected to an actuator bellows 60 by way of a capillary tube 61. The manner in which thermostat 58 controls the operation of the motors of compressor 20 will be most readily understood by reference to FIGURE 4.

Each of motors 36 and 38 which are drivingly connected to crankshaft 30 are electrically connected in par allel relation to each other and serially connected to a power source 62 upon closure of contactor switch 64. Motors 40 and 42 which are drivingly connected to crankshaft 32 are electrically connected in parallel with each other and serially connected to power source 62 by Way of motor contactor switch 66.

As the temperature within space 12 increases, the fluid within the sensing bulb of thermostat 58 exerts a pressure on bellows 60 causing bellows 60 to expand. At a predetermined temperature bellows 60 expands sufficiently to close thermostat contacts 68 thereby energizing the contactor coil 69 to close contacts 64 thus completing the power circuit to motors 36 and 38 whereby compressor 20 operates at one-half its full capacity. If desired delay means may be employed to stagger the starting of motors 36 and 38 to avoid high surge currents in the power line. If the capacity of refrigeration system is insufficient the temperature within space 12 may rise to a second predetermined level at which time thermostat bellows 60 will close contacts 70 thereby energizing second contactor coil 71 to close contacts '66. This completes a second power circuit to motors 40 and 42. The additional operation of motors 40 and 42 causes compressor to operate at full capacity. In similar manner if the temperature within space 12 should fall below said second predetermined level, compressor motors 40 and 42 will be de-energized thereby reducing the capacity of compressor 20 to onehalf its full capacity.

It should be appreciated that other forms of capacity control may be used in conjunction with the capacity control above described. Such other forms of capacity control may include means for unloading individual cylinders or groups of cylinders which are associated with crankshaft 30 such as by lifting suction valves or by bypassing discharge gas to suction.

It will thus be seen that the above described compressor and motor arrangement permits a novel means of controlling the capacity of a refrigeration system. It will also be evident that very large motor compressor units may be constructed utilizing the running gear such as pistons, connecting rods, oil pumps, etc. that are utilized on compressors having substantially smaller capacities. Furthermore, it should be evident that a substantial cost savings may be realized in the construction of large compressors by utilizing a plurality of smaller drive motors which may be purchased at a lower cost per horsepower than large motors produced in small quantities. Further the weight and size of the compressor housing is substantially smaller than the sum of separate motor compressor units totalling the same capacity.

A further advantage of my compressor over the use of several separate compressors is also clear. When less than all of several separate compressors disposed in parallel relationship within a refrigeration system are operated to obtain reduced capacity, lubricant oil will often accumulate in the crankcase of the inactive compressor and starve the active compressor of sufficient lubrication thereby causing failure of one of the compressors. To solve this problem many patented schemes have been employed to return lubricating oil from the inactive compressor to the operating compressor. It will be evident that no such problems exist in the compressor which I have shown and described as only one crankcase and oil sump is associated with the two crankshafts.

Having now described the preferred embodiment of my invention I contemplate that many changes may be made without departing from the scope or spirit of my invention, and I accordingly desire to be limited only by the claims.

I claim:

1. A refrigeration system comprising: a refrigerant compressor, a refrigerant condenser, a refrigerant throttling means, and a refrigerant evaporator respectively connected in a closed refrigerant circuit; said compressor comprising: a compressor main housing having a crankcase; a first elongated crankshaft mounted within said crankcase for rotation about a generally horizontal first axis; a second elongated crankshaft mounted within said crankcase for rotation about a generally horizontal second axis disposed generally parallel to and horizontally spaced from said first axis; a major portion of each of said first and second crankshafts being axially coextensive with the other; a first plurality of cylinders in said housing disposed above said first and second axes; a second plurality of cylinders in said housing disposed above said first and second axes; first piston means slidably mounted within the cylinders of said first plurality of cylinders; second piston means slidably mounted within the cylinders of said second plurality of cylinders; first connecting rod means for connecting said first piston means to said first crankshaft; second connecting rod means for connecting said second piston means to said second crankshaft; and means for selectively driving one or both of said crankshafts in response to the load on said refrigeration system.

2. A refrigeration apparatus comprising: a compressor main housing; a first elongated crankshaft mounted within said housing for rotation about a generally horizontal first axis; a second elongated crankshaft mounted within said housing for rotation about a generally horizontal second axis disposed generally parallel to and horizontally spaced from said first axis; a major portion of each of said first and second crankshafts being axially coextensive with the other; a first plurality of cylinders in said housing disposed above said first and second axes; a second plurality of cylinders in said housing disposed above said first and second axes; first piston means slidably mounted within the cylinders of said first plurality of cylinders; second piston means slidably mounted within the cylinders of said second plurality of cylinders; first connecting rod means for connecting said first piston means to said first crankshaft; second connecting rod means for connecting said second piston means to said second crankshaft; and means for rotatably driving one of said crankshafts independently of the other of said crankshafts.

3. The apparatus as defined by claim 2, including a first electric motor disposed adjacent and drivingly connected to a first end of said first crankshaft; and a second electric motor disposed adjacent and drivingly connected to a first end of said second crankshaft.

4. The apparatus defined by claim 3 wherein said first ends of said first and second crankshafts are remote ends.

5. The apparatus as defined by claim 3 wherein said first ends of said first and second crankshafts are adjacent ends.

6. The apparatus as defined by claim 5 including a third electric motor disposed adjacent and drivingly connected to a second end of said first crankshaft; and a fourth electric motor disposed adjacent and drivingly connected to a second end of said second crankshaft.

7. The apparatus as defined by claim 5 including a housing common to and surrounding both of said first and second electric motors.

8. The apparatus as defined by claim 1 or 2 wherein said main housing is a pair of substantially allochiral shells hermetically connected along their rims.

9. A refrigeration apparatus comprising: a compressor main housing; an elongated drive shaft mounted within said main housing for rotation about an axis; a plurality of cylinders in said housing; a plurality of fluid displacement means mounted within said cylinders of said plurality of cylinders; connecting means for connecting said fluid displacement means to said drive shaft; a first electric motor disposed adjacent and drivingly connected to a first end of said drive shaft; a second electric motor disposed adjacent and drivingly connected to a second end of said drive shaft; said main housing having a first section at one end thereof hermetically enclosing said first motor and a second section at the other end thereof hermetically enclosing said second motor; and a compressor suction inlet opening in each of said housing sections whereby refrigerant suction gas cools each of said electric motors.

References Cited UNITED STATES PATENTS 868,362 10/1907 Priest 230-58 2,012,704 8/1935 Anderson 230-58 10 2,373,779 4/1945 Ricardo 230-184 FOREIGN PATENTS 1,263,951 5/1961 France.

5 ROBERT M. WALKER, Primary Examiner US. Cl. X.R. 

